JPS6249812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control system for an AC-DC-AC power converter in which the DC sides of a forward converter and an inverse converter each configured of a controlled rectifier are connected via a DC reactor.

FIG. 1 shows a block diagram of a conventional device.

In the figure, 1 and 2 are AC power supplies, 11, 1
2, 21, and 22 are converter transformers, 13,
14, 23, and 24 are three-phase bridge-connected converters composed of controlled rectifiers, and for the sake of explanation, 13 and 23 are assumed to be forward converters, and 14 and 24 are assumed to be inverse converters.

15 and 25 are DC reactors, 16 and 26 are voltage dividers for detecting DC voltage, 17 and 27 are current transformers for detecting AC current, 1
8 and 28 are DC current detection circuits that rectify the secondary current of the current transformer 17 or 27 to obtain an AC current detection value, 41 is a DC current setting device that determines the DC current of the power converter, and 42 is a DC current setting value. A constant current control circuit 43 inputs the outputs of the DC current detection circuits 18 and 28 to control the output of the DC current detection circuit by comparing the DC current detection value with the DC current detection value and controlling the DC current to be equal to the DC current setting value. A maximum value priority circuit outputs the larger one to the constant current control circuit 42, and 44 is a DC current balance control circuit, where the forward converter 13
A power conversion group including the DC reactor 15 and the inverse converter 14 is group A (hereinafter simply referred to as group A), and a power conversion group including the forward converter 23, DC reactor 25, and inverse converter 24 is group B (hereinafter simply referred to as group B). It is a circuit that controls so that the DC currents of groups A and B are balanced.

45 and 46 are phase control circuits which receive the output of the balance control circuit 44, that is, the phase control signal, and provide a firing pulse to the control rectifier of the forward converter 13 or 23 at a phase corresponding to the phase control signal;
7 is a DC voltage setting device that determines the DC voltage of the power conversion device; 48 is a constant voltage control circuit that compares the DC voltage setting value and the DC voltage detection value and controls the DC voltage to be equal to the DC voltage setting value; 49 is voltage divider 1
A maximum value priority circuit compares the detected DC voltage values of 6 and 26 and outputs the larger one as a detected DC voltage value. A phase control circuit which provides firing pulses to the control rectifier of the inverter 14 or 24 with a corresponding phase.

In the power converter configured as described above, the DC output voltages of the inverters 14 and 24 are determined by the DC voltage setter 47.

On the other hand, the DC current is controlled by a constant current control circuit 42 to be the set value of the DC current setting device 41. That is, the DC voltages of groups A and B are determined by the DC voltage setting device 47, the DC currents of groups A and B are determined by the DC current setting device 41, and the converted power of the power converter is determined. .

What should be noted here is that the DC voltage and DC current are detected from each group, and the maximum value priority circuits 48 and 43 give priority to the detected value of the DC voltage and DC current, whichever is larger. The detected value is input to the constant voltage control circuit and the constant current control circuit. This is because if the larger value of both DC voltage and DC current is controlled as the detected value, it is safe from overvoltage and overcurrent. However, if the detection value is the larger value like this, it is either group A or group B.
A failure occurs in current control when a group inverter 14 or 24 fails to commutate. For example, if the inverter 14 of group A fails in commutation, the DC output voltage of the inverter 14 temporarily becomes zero, so
The group current increases transiently. As a result, the direct current of group A becomes larger than the direct current of group B, so the maximum value priority circuit 43 gives priority to the direct current of group A and inputs it to the constant current control circuit 42. As a result, the DC output voltages of the forward converters 13 of group A and the forward converters 23 of group B decrease in an attempt to reduce the DC current, but since the DC output voltage of the inverter 24 of group B is normal, The direct current of the group decreases. At this time, the balance control circuit 44 normally operates,
It would be good if the DC current of group B did not decrease, but in reality, the response of the balance control circuit cannot be very fast in order to stabilize control during steady state of balance control, so the balance control circuit does not prevent commutation failure. B cannot fully respond to the rapid change in DC current caused by
The DC current of the group will decrease, and there is a risk that the DC current will become intermittent. In a power converter that transmits power from a forward converter to an inverse converter via a DC reactor, if the converter is configured with a controlled rectifier, abnormal voltage will occur if the DC current is interrupted, so It is generally well known that there is a problem in which a group that fails to flow has no choice but to stop.

As described above, the conventional system has the disadvantage that when commutation failure occurs in one group, the DC current on the healthy side of the other groups becomes intermittent.

An object of the present invention is to provide a control method for a power converter in which two or more groups of power converters are operated in parallel, and which prevents DC current in other groups from intermittent when one group of inverters fails to commutate. It is about providing.

Hereinafter, the present invention will be explained with reference to the drawings. Second
The figure shows a block diagram of an embodiment of the present invention.
Fig. 2 shows current transformers 19 and 29 for detecting alternating current and rectifying the secondary current of current transformer 19 or 29 to obtain an alternating current detected value, in contrast to Fig. 1 explained as a conventional method. DC current detection circuits 20 and 30 and current transformers 17 and 2 as DC current detection values
A configuration in which commutation failure detection circuits 52 and 53 are added to detect commutation failure of the inverse converter by comparing the current of the forward converter detected in 7 and the current of the inverse converter detected in current transformers 19 and 29. Furthermore, a function is added to the phase control circuits 50 and 51 to apply a firing pulse to the inverter so that the inverter becomes a DC short circuit in response to signals from the commutation failure detection circuits 52 and 53. A method of controlling an inverse converter so that it becomes a DC short circuit is a known technique that is used as bypass pair control in power conversion devices such as DC power transmission and frequency conversion devices.

Next, the operation of the present invention having the above configuration will be explained. In FIG. 2, for example, the inverter 14 of group A
When commutation fails, the commutation failure detection circuit 52 detects the commutation failure and outputs a signal to the phase control circuit 51 of group B. The phase control circuit 51 receiving the signal from the commutation failure detection circuit 52 sends the signal to the B group inverter 24 in such a way that the inverse converter 24 becomes a DC short circuit, which is the same as the commutation failure of the A group inverter 14. Give an ignition pulse that causes the phenomenon. As a result, the direct current in group B increases in the same way as in group A, and it is possible to prevent the direct current from intermittent. Incidentally, if the commutation of group B fails, the inverter 14 of group A can be short-circuited in the same manner as described above, thereby preventing the DC current from intermittent.

To summarize the above, if one group operating as a reverse converter fails in commutation, the other remaining groups are also forced to fail in commutation, thereby preventing intermittent DC current. Can be done.

In addition, in an inverter, commutation failure is a temporary phenomenon and can be recovered naturally, so even if a healthy group is forced to fail in commutation as described above, there will be no problem in the operation of the power converter. do not have.

As explained above, the present invention prevents the interruption of DC current in other groups when commutation failure occurs in one group of inverters of two or more groups of power converters operated in parallel, thereby causing the commutation failure. It is possible to provide a control method for a power converter device that can prevent a group that has not grown up to a halt and can improve the utilization rate of the power conversion system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1, 2... AC power supply, 11, 12, 21, 22
...Transformer for converter, 13,23...Forward converter,
14, 24... Inverter, 15, 25... DC reactor, 16, 26... Voltage divider, 17, 27...
...Current transformer, 18, 28...DC current detection circuit, 1
9, 29... Current transformer, 20, 30... DC current detection circuit, 41... DC current setting device, 42... Constant current control circuit, 43... Maximum value priority circuit, 44...
Balance control circuit, 45, 46... Phase control circuit, 47... DC voltage setter, 48... Constant voltage control circuit, 49... Maximum value priority circuit, 50, 51...
...Phase control circuit, 52, 53... Commutation failure detection circuit.

Claims (1)

[Claims] 1 At least two groups of AC-DC-AC power converters, each consisting of a forward converter composed of a controlled rectifier and the DC side of an inverse converter connected via a DC reactor, are installed to convert the DC current and DC voltage of each group. detect,
In a power conversion device in which the maximum value of these detected values is applied as a feedback signal to a constant current control circuit and a constant voltage control circuit common to each group to control the current and voltage of each group, an inverter is used. By providing each group with a commutation failure detector for detecting a failure in current flow, and applying the output signal of the commutation failure detector of the own group to the phase control circuit of the inverter of the other group, A control method for a power converter device, characterized in that when an inverter in its own group fails in commutation, inverters in another group are placed in a bypass pair state.